<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<div style="text-align: center"><h3>今天吃什么</h3>
    <button onclick="ttt()">按钮</button>
    <div id="msg"></div>
</div>
</body>
<script>
    function ttt() {
        let a  = ['饺子','食堂','面馆','黄焖鸡','余百年','炒菜']
        document.getElementById('msg').innerHTML = '<h1>'+a[new Date().getMilliseconds()%a.length]+'</h1>'
    }

</script>
</html>